A typical modem of an electronic device includes a symbol detector for determining log-likelihood-ratio (LLR) values of coded bits from received signals. These LLR values are used by a decoder of the modem to recover uncoded bits. When the number of layers (i.e., the rank) used for multiple-input multiple-output (MIMO) transmission increases, the complexity of symbol detection may increase significantly. In long term evolution (LTE) (Release 10) and fifth generation (5G) (Release 15), a maximum of eight transmit and eight receive antennas or panels are supported. Accordingly, 8×8 or rank-8 symbol detectors are required.
Existing MIMO symbol detectors include, for example, maximum likelihood (ML), zero-forcing (ZF), minimum mean square error (MMSE), ZF/MMSE-successive interference cancelation (MMSE-SIC), and sphere decoder (SD) detectors. For high rank scenarios, such as rank-8, existing linear symbol detectors, such as, for example, ZF and MMSE detectors, have degraded performance due to their simple architecture. Existing non-linear symbol detectors, such as, for example, ML, ZF/MMSE-SIC, and SD detectors, may perform well but are too complex to be implemented. For example, ML detection requires that all symbols in a constellation are considered for LLR value calculation.